Inflatable restraint systems utilizing an airbag and inflator are widely accepted in all types of vehicles. Vehicles have differing characteristics; for example, vehicles differ in the size and configuration of their dashboards or other mounting points for inflatable restraint systems, vehicles differ in the distance between the dash and an occupant of the vehicle, and vehicles differ in the width or height for which airbag protection is desired. Vehicles further differ in their structural response to crashes and in the sensor input provided to the inflators. These differences create variables in the restraint system, such as the shape and volume of the airbag and the desired speed of its deployment. Those variables in turn create different requirements of inflators supplying inflation gas to the bags. Some of these requirements have been addressed by hybrid inflators, which utilize a combination of stored compressed gas and a pyrotechnic gas generant material. The pyrotechnic gas generant provides some of the inflation gasses and also heats and expands the stored gas to enhance its contribution to inflating the bag.
The size of a hybrid inflator is in part determined by the volume of stored compressed gas, as well as the configuration and content of the pyrotechnic gas generant component. It further depends upon the volume of screen and filtering material required to trap particles and hot debris resultant from operation of a pyrotechnic gas generant system, as it is undesirable to introduce hot particles of burning gas generant and inflator debris into the expanding airbag. Further, passenger side hybrid inflators deliver gas from the end of an elongated housing, which detracts from even inflation of an airbag.
With due consideration for the aforementioned requirements of occupant restraint systems, it is desirable to decrease the size, weight and complexity of the inflators, and to provide for efficient delivery of inflation gas to airbags. It is further desirable to be able to adjust the performance parameters of inflators by building on established research, development and manufacturing capability.